Japan Weighs Wider Evacuation Zone

By

Toko Sekiguchi and

Mitsuru Obe

Updated April 8, 2011 12:01 a.m. ET

TOKYO—Japan's government said Thursday it is considering extending the evacuation zone around its hobbled Fukushima Daiichi nuclear complex, as the government recalculates the risk of radioactivity that continues to issue from the plant four weeks after Japan's devastating earthquake and tsunami.

Later on Thursday, Japan suffered its strongest temblor since the March 11 quake, highlighting the ongoing uncertainty over whether further aftershocks could damage the reactors further and release more radiation, or put other nuclear plants at risk. Some other plants were running on emergency generators but no operating problems were reported in the hours after the 7.1-magnitude quake.

Workers are injecting nitrogen into a Fukushima Daiichi reactor, in the latest effort to get the nuclear situation under control, while the nuclear disaster in Japan is becoming an increasingly important issue in American politics.

The government's top spokesman, Chief Cabinet Secretary Yukio Edano, said Thursday the current 20-kilometer (12-mile) evacuation zone around the Fukushima Daiichi plant may need to be enlarged, because the original parameters were established to protect against too much exposure in the short term and radiation continues to emanate from the complex.

Officials intended the evacuation zone to prevent anyone getting more cumulative exposure to radiation than a nuclear plant worker is limited to in a year—50 millisieverts.

"Current evacuation orders apply to areas where people are in danger of having received 50 millisieverts [of cumulative exposure]," Mr. Edano said. "We are now looking into what to do with other areas where, with prolonged exposure, people may receive that amount."

ENLARGE

Japanese police, wearing suits to protect them from getting contaminated with radioactive materials, search for victims inside the evacuation zone around the Fukushima Daiichi nuclear reactors on Thursday. Japanese officials are considering widening the zone.
Associated Press

Two weeks ago, a state-funded monitoring body released a computer simulation that showed that in the first 12 days of troubles at the plant, certain areas beyond the evacuation zone had exceeded Japan's recommended cumulative exposure.

The body, the Nuclear Safety Commission of Japan, hasn't released an updated assessment since. A commission official said Thursday the group is collecting more data to improve the quality of its model.

Tepco said it has provided radiation figures from several locations near the complex and is awaiting government analysis before making the data public.

The government hasn't said when it would make a decision on expanding the zone, what measures it would use or how it might house those it relocates. It said it hasn't set a timetable.

The discussion is likely to renew international scrutiny of the government's 20-kilometer (12-mile) zone, which is smaller than 80-kilometer (50-mile) zone recommended by U.S. officials.

Several municipal officials in the area expressed anger at the government's handling of the situation. The mayor of one town just outside the 30-kilometer radius said the government should have thought ahead earlier in the crisis.

"We are hearing that it may take months for the plant to settle down—and only now are they talking about expanding the zone?" said Michio Furukawa, mayor of Kawamata, a town to the northwest with elevated radiation levels that is one of seven municipalities from which sales of local produce have been banned. "When this will all end?"

ENLARGE

Last week, the government reported that just a handful of people have remained inside the 20-kilometer exclusion zone. It said thousands remain in the band 20 to 30 kilometers from the plant, where the government has urged residents to remain indoors as much as possible. It said others travel into the band daily to check on people and property.

Senior nuclear regulator Hidehiko Nishiyama apologized for the possible further dislocation to those living in the area. He identified a series of hydrogen explosions at the plant days after the earthquake as the primary cause of the widespread radiation.

"The explosions sent radioactive materials flying to areas far outside the nuclear complex," Mr. Nishiyama, of Japan's Nuclear and Industrial Safety Agency, said at a news conference. "Radioactive materials, once spread, cannot be put back. The best we can do is to stabilize the damaged reactors and prevent further emissions of radiation."

The U.S. Nuclear Regulatory Commission, in a March 26 assessment of the plant that was made public this week, said a hydrogen explosion in a spent-fuel cooling pool threw particles of nuclear fuel up to a mile from the complex.

An NRC spokesman said it is "not our place" to comment on Mr. Edano's remarks on possibly widening the evacuation zone. "The Japanese government makes its decisions based on what they consider appropriate for their citizens," the spokesman said.

In the hours after the late Thursday quake, NISA said the Fukushima Daiichi plant hadn't reported immediate problems but that it was sending workers to check on the status of its reactors.

In an effort to head off further hydrogen explosions, the plant operator, Tokyo Electric Power Co., early Thursday began streaming nitrogen gas into reactor No. 1, one of the less damaged of the three crippled units. Tepco said these operations continued Friday morning.

Reactor No. 1's pressure and containment vessels are seen to have come out relatively unscathed by the overheating of the reactor core following the failure of the cooling system on March 11.

However, as the fuel cooled down and more steam condensed into water, fears grew that the pressure inside the containment vessel would fall sharply, allowing air to come in and create a dangerous mix of hydrogen and oxygen. Nitrogen injection is designed to forestall the entry of oxygen.

Reactor Update

"The injection of gas is proceeding smoothly," a Tepco company official said at a briefing. The process began around 1 a.m. local time Thursday and will continue for about six days, he said, adding that the measure was having the desired effect of slightly raising the pressure within the container vessel.

Tepco also said that its president, Masataka Shimizu, had returned to work after being hospitalized for more than a week as his company was blamed for power outages and radioactive contamination that swept eastern Japan.

Mr. Shimizu will assume the role leading a joint task force with the government to support evacuees, allowing Chairman Tsunehisa Katsumata to continue his role of overseeing the company's effort to bring the plant under control, according to Tepco spokesman Naoyuki Matsumoto.

The other two heavily damaged units—reactors Nos. 2 and 3—stayed in a relatively stable condition Thursday, as workers continued to pump cold water to cool the reactor cores.

ENLARGE

The Fukushima Daiichi nuclear power plant Monday, as seen from the deck of a U.S. military barge hauling water
Japan Ministry of Defense via Bloomberg News

The recovery efforts have received some support from the British government, which said it was easing its travel restrictions to Tokyo based on its scientific analysis of the current situation.

"Although the situation at Fukushima will remain of concern for some time, the risks are gradually declining as the reactors cool and as facilities to stabilise them are established," the government's Foreign and Commonwealth Office said on its website.

Corrections & Amplifications

The white protective gear Japanese police wore while searching for victims inside the evacuation zone around the Fukushima Daiichi nuclear reactors is designed to protect them from getting contaminated with radioactive materials. A photo caption that accompanied an earlier version of this article incorrectly said the suits protected the police from radiation.

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